1. Field of the Invention
This invention relates a rocket engine cycle that generates high velocity and high specific impulse discharge gas with a fluid such as liquid hydrogen.
2. Background
Liquid propellant rockets can traditionally classified into two families, pressure-fed and pump-fed. There are advantages and disadvantages to both families
Pressure-fed engines require that a pressurizing fluid be used to maintain pressure in the primary propellant tank as the fluid is drained. To operate such a system at sufficient pressures and flow rates, the pressure in the primary propellant tank must be high. This mandates thick-wall construction and consequently, for large systems, very heavy propellant tanks. Thus, this is a simple design but is often limited in size for practical application.
Pump-fed engines avoid the need for thick-walled propellant tanks and, sometimes, the necessity for separate pressurization systems. In this configuration propellant from a low-pressure propellant tank is fed into a pump in which its pressure is raised thereby feeding it through the rest of the system. One problem with such a system is the need for a system to power and drive the pump. Also, there are intrinsic reliability issues with regards to all rotating machinery particularly if expected to operate for long periods and at high rotational speed.
What is desired is a rocket system that has the features of simplicity associated with the pressure-fed system with the compactness and lighter weight associated with a pump-fed system.
The standard rocketry literature is rife with examples of nuclear thermal rocket engine cycles. Additionally, a number of U.S. Patents exist for both nuclear thermal rocket engine cycles and, in a related vein, for solar thermal rocket engine cycles, such as U.S. Pat. Nos. 6,412,274; 6,343,464; 6,290,185; 5,873,239; 5,636,512; 5,475,722; 5,410,578; 4,246,751; 4,147,590; 3,820,325; 3,817,029; 3,793,832; 3,778,344; 3,336,749; 3,286,468; 3,168,807; 3,150,054; 3,108,054; and 2,917,443, each of which is hereby incorporated by reference in its entirety. There also exist a number of U.S. Patents in the area of innovative pressurization schemes for rocket engine application, such as U.S. Pat. Nos. 6,499,288; 6,314,978; 5,531,067; 5,251,852; 5,207,399; 5,205,722; 4,880,185; 3,672,165; 3,213,804; and 3,136,121, each of which is hereby incorporated by reference in its entirety.
A conventional system is disclosed by U.S. Pat. No. 6,499,288 (herein incorporated by reference in its entirety). Therein, is included a pressurizer for pressurizing a fluid, comprising a pressurant entrance for the introduction of a pressurant, a fluid entrance for the fluid, a fluid exit for the fluid, and a transfer chamber movable in a cycle with respect to the fluid exit, where for a portion of a cycle the pressurant exerts a force on the fluid inside the transfer chamber. In a preferred aspect of the disclosure, the pressurizer further comprises a spindle housing more than one transfer chamber, rotatable about an axis between the fluid entrance and the fluid exit. In another preferred aspect, the transfer chamber comprises either a flexible membrane or a movable piston to separate the pressurant and the fluid. In another preferred aspect, the pressurizer further comprises a pressurant exit for a pressurant exhaust. In preferred aspect disclosed therein, the pressurant exhaust is exhausted in a direction substantially opposite a direction of motion of the transfer chamber. In another preferred aspect, the pressurizer further comprises a motor to move said transfer chamber. In another preferred aspect, a cross section of the pressurant entrance is larger than a cross section of the fluid exit, and a cross section of the pressurant exit is larger than a cross section of the fluid entrance. In another preferred aspect, a cross section of the fluid entrance is greater than a cross section of the fluid exit.
The rocket engine system of this reference includes a pressurant, a pressurant container, a propellant, a propellant container, a rocket engine, and a transfer chamber movable in a cycle with respect to the rocket engine, where for a portion of a cycle the pressurant exerts a force on the propellant inside the transfer chamber. In a preferred aspect, for a portion of a cycle a bouyant force causes the propellant to flow into, and the pressurant to flow out of, the transfer chamber. In another preferred aspect, the rocket engine system further comprises a heating means for heating the pressurant, where the heating means comprises a heat conductor for conducting heat from the rocket engine to the pressurant. In another preferred aspect, a pressurant exhaust exerts a force on the propellant inside the propellant container. In another preferred aspect, the propellant comprises an oxidizer and a fuel. In another preferred aspect, the rocket engine system further comprises an engine conduit between the transfer chamber and the engine and a propellant conduit between the transfer chamber and the propellant container, where a cross section of the propellant conduit is greater than a cross section of the engine conduit. However, in this type of system the pressurizing fluid is stored, high-pressure gas, in contrast to the present invention.